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Events

This tutorial will help you with creating Events in Device Templates

Getting Started -> Events

Events are used to track, log, and work with important events that happen on the device.

Events are also used for notifications which can be sent over email, delivered as push notifications to user's smartphone, or sent as an SMS.

Events are pre-configured in Blynk.Console and can be triggered with a Events Firmware API from device or using Events HTTP API.

Examples of an Event:

  • Log a moment when a temperature reached a certain threshold and send a notification to selected users

  • Track total working hours of the device. If it approaches or goes beyond a max value, you would need to notify technical support so that they can replace the device or provide warranty service

Events list in the template

Types of Events

There are three types of Events in Blynk:

  • System Events: Default Blynk platform events.

  • Custom Events: Events you can create and configure for your needs

  • Content Events: Informative events that are shown separately in the app

System Events

You can't delete the system events, but you can configure them.

Online/Offline status

This event is used to track when devices goes online and offline.

In some cases you would need to ignore offline state for a certain period of time. For example, if your device is mostly offline (or in deep sleep) and only wakes up every hour to send the data.

Firmware Over-The-Air Update status

This is a system event to track firmware update. It can't be configured

Custom Events

These are Events you can configure based on what your device do. Read these articles to start logging events and sending notifications:

How to log an event in Blynk

1. Create a Template or use an existing one

2. Create a New Event

Go to Template -> Edit -> Events tab.

  1. Click Add New Event

  2. Name the first event with the name Hello

  3. Click Create (the event will appear in the Events tab list)

  4. Repeat the previous step for the second event with the name Error

  5. Click Save to save and apply the changes made (select Update active device this time)

Note that each event hasEVENT_CODE. This event code will be used in firmware API or HTTPS API

Send Events Using Firmware API

  1. Create a new Event named High temperature with code high_temp

  2. Use the Blynk.logEvent(event_code) firmware API command to trigger new event

if (temperature > 35)
{
   Blynk.logEvent("high_temp");
}

When this code worked, an Event will be logged and the system will act accordingly to the Event setup (render on timeline, send notifications, etc.)

Avoid logging an event too many times not to hit daily limits. You can use timers or flags to mark the already sent events. Check this article on how to avoid spamming the server with events

Custom Event Description

You can change the description of the event when it's rendered on the timeline in Blynk.Console and in Blynk.Apps. For example, you can include the current data

if (temperature > 35)
{
  Blynk.logEvent("event_code", String("High TemperatureDetected! Tº: ") + temp);
}

Make sure you enabled Timeline recording in the Event Settings to see the result in the apps

Send Events Using HTTPS API

To log an event use GET request: 

`/external/api/logEvent?token={AuthToken}&code={event_code}

To add custom description to the event, use this GET request

`/external/api/logEvent?token={AuthToken}&code={event_code}&description={event_description}

Example:

https://blynk.cloud/external/api/logEvent?token=GVki9IC70vb3IqvsV0YD3el4y0OpneL1&code=firmware_update&description=test

3. Sending Events

You can test the Event creation by sending it from Device using Blynk.Edgent firmware API, or with REST API.

Use Blynk.logEvent() firmware API

Blynk.logEvent("event_code", "optional message");

For this tutorial you would need to use hello as a name. Here is a pseudo code:

if (some_condition){
    Blynk.logEvent("hello");
}

Optionally, you can send a custom description with the event. This description will be rendered on Device Timeline.

if (some_condition){
    Blynk.logEvent("hello", "Hello World,") ;
}

Use HTTP REST API

  1. Navigate to the Device

  2. Click on its name

  3. Open Device Info tab

  4. Find Auth Token there and click on the icon to copy it to the clipboard

Auth Token. Click copy pictogram here

Now make an HTTP request with the tools you use for that. Make sure to change the YourAuthToken to the one you copied in the previous step.

You can even use your browser for that. Just put it in the URL field and press Enter.

https://blynk.cloud/external/api/logEvent?token=YourAuthToken&code=hello

Repeat the same with code=error

https://blynk.cloud/external/api/logEvent?token=YourAuthToken&code=error

4. Checking if Event was logged.

First of all, check Device Timeline by going to Device - > Timeline Tab

You should see 2 events on the timeline! If you set up notifications, they should have been delivered as well.

Limitations

  • You can send only 100 events per devices per day (Adjustable in Business Plan)

  • When the limit is reached you'll see the notification on the UI in the Device Timeline section

  • The maximum description length for the event is 300 characters

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